FIG. 1 shows an example of a combustion turbine engine 10. The turbine engine 10 includes a compressor section 12, a combustor section 14, and a turbine section 16. The combustor section 14 can include a plurality of combustors 18 (only one of which is shown) arranged in an annular array around a rotor. The turbine section 16 includes alternating rows of stationary airfoils 20 and rotating airfoils 22.
In operation, air is drawn in through the compressor section 12, where it is compressed and driven towards the combustor section 14. The compressed air 24 can be distributed to the plurality of combustors 18. The air 24 can be mixed with fuel to form an air/fuel mixture. In each combustor 18, the fuel/air mixture can be ignited to form a working gas 25. A duct 26 (sometimes referred to as a transition) can be provided for each combustor 18 to receive the hot working gas 25 therefrom. The duct 26 can route the working gas 25 to the turbine section 16. The transition duct 26 has an inner peripheral surface 28 and an outer peripheral surface 30. The inner peripheral surface 28 of the transition duct 26 defines the flow path for the hot working gas flowing therethrough.
The transition ducts 26 are typically monolithic structures that are made of a single material. However, such a construction is not well suited for the various operational loads expected to be imposed on the transition duct 26. For instance, the inner peripheral surface 28 of the transition duct 26 is exposed to the highest temperatures of combustion and combustion dynamics and, as a result, is susceptible to damage therefrom. On the other hand, the outer peripheral surface 30 of the transition duct 26 is not directly exposed to the hot working gas path and therefore will be less directly impacted by the high combustion temperatures and combustion dynamics. However, the outer peripheral surface 30 is equipped with mounting and sealing structures and must be able to withstand the associated mounting and sealing loads imposed thereon.
Thus, the inner and outer peripheral surfaces 28, 30 of the transition duct 26 are subjected to different types and amounts of loading during engine operation. If the material of the transition duct 26 is selected based mostly on the expected loads imposed on the inner peripheral surface 26 thereof, the selected material may be less than optimal for the kinds of loads experienced at the outer peripheral surface 30. Thus, there is a need for a system that can minimize these concerns.